Please am new to ppsspp and all and I am using a phone of version 7.1 nogut and I don't know how to get ppsspp games or iso game file to run the game so anyone tell me how to get games to run on ppsspp

PSP games can be bought digitally from PS Store, from anyone that still sells PSP UMD's. In the first case you will need to download a pkg file, then just extract a PBP file from it and that's pretty much best disc backup format you can get which PPSSPP can read. In case of UMD's, you will have to use real PSP with custom firmware to dump the game(by mounting UMD drive for usb) to another device.